This invention relates to methods and compositions for inhibiting deposit formation on contact lenses. More particularly, the invention relates to methods and compositions for inhibiting the formation of proteinaceous deposits and/or lipid deposits on contact lenses being worn in mammalian, preferably human, eyes.
The use of contact lenses for vision correction is widespread and provides substantial advantages. However, one problem that is apparent is the lack of comfort in wearing contact lenses over long periods of time, even though the lenses themselves are removed from the eye on a regular and frequent basis. One reason for this eye discomfort and irritation is the formation of deposit material on the contact lenses during wear. Such deposit material, which often has its origin in proteinaceous and/or lipid material from the eye of the contact lens wearer, becomes deposited on the contact lens and creates irregularities on the surface of the lens which tend to cause eye discomfort and/or irritation.
One approach to removing the deposit material from a contact lens is to clean the lens of such deposit material while the lens is outside of the eye and not in use. Examples of this "outside the eye" cleaning approach are set forth in Chanda et al U.S. Pat. No. 4,715,899 and Ogata U.S. Pat. No. 4,285,738. Chanda et al teaches the concurrent use of an aqueous solution containing an inactivated sulfhydryl protease (an enzyme) and an aqueous thiol reducing agent, such as glutathione, to remove protein soil from contact lenses outside the eye. Ogata et al teaches removing proteinaceous material from contact lenses outside the eye by immersing the lenses in an aqueous hypotonic composition including urea or a salt of guanidine and a reducing agent, such as glutathione. Neither of these patents even suggest using these compositions in the eye. The enzyme-containing composition of Chanda et al and the protein denaturant-containing, hypotonic composition of Ogata et al are not ophthalmically acceptable and may even cause substantial ocular damage if placed in the eye.
The approach of removing proteinaceous deposit material from a contact lens outside the eye, although very useful, does require an additional step to be implemented by the wearer of the contact lens. It would be advantageous to provide a system whereby the formation of deposit material on a contact lens is inhibited during use of the contact lens.
Removing already formed deposit material from a contact lens is an entirely different phenomenon from inhibiting the formation of deposit material on a contact lens. An agent known to be useful in removing already formed deposit material is not obviously effective in inhibiting the formation of such deposit material in the first place. This is particularly true if the deposit removal is to be effected outside the eye and the inhibition of deposit formation is to occur while the lens is being worn in the eye.
Of course, any components or materials which are to be used while the contact lens is in the eye must be ophthalmically acceptable. By "ophthalmically acceptable" is meant that a material has substantially no detrimental effect on the mammalian eye into which it is placed.
Japanese patent application JP-196378 discloses an eye lotion useful as a remedy for cataract. The lotion contains oxidized glutathione as a prodrug for reduced glutathione which plays a role in maintaining transparency of the natural crystalline lens. This patent application does not disclose any effect of the eye lotion on the wearing of contact lenses.
Japanese patent application JP-011497 discloses ophthalmic compositions for treatment of corneal diseases which contain oxidized form glutathione or its salts as principal components. These compositions are disclosed as having a pH which is adjusted at 5.0 and as being useful for the treatment of corneal diseases, e.g., keratitis. This application teaches that conventional auxiliaries may be added, for example, polyvinyl alcohol as a thickener. This application does not teach or suggest any effective use of such compositions in contact lens care.
Garabedian et al U.S. Pat. No. 4,443,432 discloses a stable sterile two part system for preparing an ocular irrigating solution for irrigating the eye during surgery. Part A involves a basic solution containing bicarbonate ion. Part B includes an acidic solution containing calcium ions, magnesium ions, dextrose and glutathione provided that one of the solutions contains sodium, potassium and chloride ions. This patent does not teach or suggest such compositions as being effective for any purpose in the contact lens care context.
Schachar U.S. Pat. No. 4,620,979 discloses a method for maintaining normal ascorbate levels in ocular tissue of an eye subjected to intraocular surgery which involves irrigating the eye with a composition comprising sodium chloride, potassium chloride, calcium chloride, magnesium chloride hydrate, sodium hydrogen phosphate, sodium dihydrogen phosphate, sodium bicarbonate, glucose, adenosine, glutathione, sodium acetate, sodium citrate, sodium lactate and ascorbate. This patent does not teach or suggest any effective use of this composition in the contact lens care context.
There continues to be a need for a system useful to inhibit the formation of deposits on contact lenses, particularly while the lenses are being worn in the eyes.